RV Repair: RV Furnace, propane tank, air furnace

Question
furnace will not fire up after filling propane tank.  T. stat calls for heat, funace fans works but no heat.  Same thing happened after running out of propane and refilling, was able to restart a day later and worked fine.  I have "bled" the propane line in case there was some air in the line.  Any ideas?

Answer
Ken,
   I am assuming you have a direct spark ignition forced air furnace since there was no mention of a pilot.  If you have sufficient voltage to the furnace, then as the fan starts it should send voltage to a sail switch, then a limit switch, then the circuit board.  The circuit board should then send voltage to the gas valve to open it and send a spark ignition to the electrode.  Any one of these could have failed.  You will need a volt meter and a wiring diagram for your furnace to follow the path and see where it's losing voltage.  I hope this helps.

Darren